Furnace



M. UNGER April 7, 1931.

FURNACE iginal Filed June l ITM/@Tibor Magnus UnQe-r, bg Ma/97M His Attorney.

Patented Apr. 7, 1931 .UNITED STATES vMAGNUS UNGEB, F

PITTSFIELD, MASSACHUSETTS, ABBIGNOB TO GENERAL ELCTBIC COHPANY, A CORPORATION 0F NEW YORK FURNACE Original application med June 1, 1928, Serial No. 282,154. Divided and this application illed April 1l',

1930. Serial No. 445,477. t

My invention relates to furnaces, more particularly to electric metal melting furnaces, and has for its object an improved method for making a rugged and eicient furnace construction whereby leakage of the molten metal is prevented.

More specifically my invention has particular reference to electric metal melting furnaces in which all or part of the metal being heated forms a closed secondary in which heating currents are induced from a primary winding arranged within the secondary. In

this type of furnace the metal is contained in a crucible which is ordinarily formed by ramming a suitable refractory material in plastic form in a suitably shaped mold, after which the crucible is suitably fired.

It has been found heretofore `that refractory crucibles, especially those formed by ramming the refractory material in a mold,

sometimes develop cracks due to unequal expansion from changes in temperature or due to local heating` and cooling. oftentimes these'cracks resulted in leakage of molten metal from the crucible. In induction furnaces there is the danger that the molten metal escaping through such cracks may form secondary loops and thus become heated by induced current. The escaping metal is thus kept li uid and tends to run further until eventuiillya serious run-out may take place. Furthermore, in ring ty y l the crucible containing t e molten'metal surrounds a refractory tube which in turn surtends to expand on'heating and thus a space is often formed between the crucible an the tube which surrounds the primary winding.

Metal leaking into this spacemay form a secondary circuit and cause trouble.

In accordance with my invention I\ pack a layer of powdered or anular refractory material about the cruci le y a metal leak occurs through a crackin the lining, the metal will be stoppedf when 1treaches the layer of granular material; f The powdered or granular material also allows relative expansion crucible and the heat insulating walls sur- 5 rounding it. Preferably, the granular or furnaces in which rounds a primary heatingcoil thefci-ucible `tory for the upper surfaces 'of thecrucibe 14 and sothat in case-,ber 16 may contain. a-

and contraction of thel powderedl material will be agitated as it is applied so that it will be compacted tightly against the crucible. It is also preferable to heat the crucible sothat the material will be packed about the walls of the crucible while they .are heated.

This application is a division of my copending application, Serial No. 282,154, filed June 1, 1928. For a more complete understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is asectional elevation of a ring ty e furnace embodying my invention; and ig. 2 is a sectional elevation showing my invention applied to a lfurnace of another type.

Referringto the' drawing I have shown luy-invention in Fig. 1 as a plied to a horizontal ring type induction urnace comprising a primary winding 10 surrounding a core 11, and ac'rucible providinga channel 12 for holdin the molten metal 13 Vwhich acts as a close secondary in which currents are induced bythe primary winding 10. They channel 12 is formed in an annular crucible 14 which may be made from a suitable refractory material, such as a mixture of fused ma y esia, calcined magnesia and a binder suc as magnesium sulphate, as described in `Patent '.No. .1,444,527xto 'Scharsclim dated lFebruary 7 1925. Thesematerials are mixed in granulated or powdered form, sucient water being added to make a` plastic mixture and the mass thus formed is rammed in place yin a suitable mold which 4defines the' crucible' 14 with its channel 12. vSurroundi 'and alsol immediately underneatlithe'cruci le 14 is a layer ing material 15 such as lire brick. A refracme'inber 16 is provided, foxminl a cover the refractory layer-f 15and this -cover memgroove 17 in register-l ing relation' l with* vthethchannfel 12.'bFor stren ening purOB, vre cover mem r 16` and ie up y r an 'outerie of the layer'- A1li 4muy be und withmotal ic strips-18, L- shape in cross section.

A metallic tubular member .19 surrounds the primary winding 10 wound on one leg of suitable refractory heat insulatv andhence'itis general practice to use an outer l layer 15 of amaterial having low heat conducof thecore 11 and between this tubular member 19 and the Crucible 14 is a layer 20 of refractory, granular material, 'such as fused magnesia rains. The granularv material 20 is ramme and packed to form a ver dense mass, and to provide means for packing this material tightly between the tubular member 19 and the crucible 14, I rovide a series of Y tion will be applied intermittently, and only solong'as the lining expands due to rising tubes 21, preferably ma e from a suitable non-magnetic material, arranged` vertically, approximately midway between the tubular member 19 and the Crucible 14. The packing ofthe granular materialv 20 'is accomplished while the metal 13 and Crucible 14 are being` heated, by vibrating the tubes 21 continuous-j` 1y by any7 suitable vibrator (not shown), such y as used 1n foundries. Preferably, the vibratemperature. This assures the compacting of the materiali tightly aga-inst the Crucible j after it hasbeenheated too j rating tempera-A tures, andi subsequently? uringY operation,

y' whereby-"leakage 'of moltenfmetal .through anyA cracks yvhich may be'formed in the cru- Cible Willbestopped. While the furnace is in operation ,thetubes'21also serve the purpose ofcoolingfanymetal leaks occurring in thecrucihle by thefpassing kcfa. cooling mef,

not necesario# i that they :beef tubular form. y Betweenthe outer peripheryr 14 andthe refractoryylayer 15 Iprovide an' o other layer 22 of the granular material suchl as usedinthelayerl'20. The space between the*` .-cruCblellhDd thvlayer 15 isffilled with theY j granular material 22 while the Crucible 14 is dium',fsucli Aas' air" lwater.o'rair with atomized 1` waarneemt stoodyof course, that the' 4members 21 may i have. any Suitable Afcoristruction and Athat it isl fthe vibratingf operation cold and this material 22'ser'v'es to take up the difference in.. expansion between the crucible 14l and `the layer'l when the Crucible is heated.

The ,crucible-v 14'r` has highheat conductivity vtiv-i ty'.f--. Y Consequently, when the furnace is a heated the rcrucible will expand:` more' thanI 1 therefractorylayer 15, and one purpose off the 7 layer'22jof` granular material is to serve as a I- 1 .material forming`-the-layers 20'Aor`22,

l l 1,71 Figi QIhave iShw-n my invention as ai).

- plied toaf furnace' of the typedisclosed ina patent infmy naine,l No. 1,628,375, dated May outer shell 3 1. Angular rings v "strengthen the outer shell 31. of the Crucible J 10, 1927. This furnace comprises an inner heat insulated Crucible 23 which is shaped to provide a reservoir 24 for the metal and an annular chamber25 in which a portion of the molten metal forms a Closed secondary for a primary winding 26 associated therewith. The annular channel 25 is horizontally arranged, i. e., with its axis substantially vertical at one side of the reservoir 24, a slight distance above the bottom of the reservoir. It is connected with the reservoir through ducts 27 and 28 provided in the refractory material of the Crucible. The Crucible 23, similar to Crucible 14 of Fig. 1, is made from a suitable refractory material, such yas a mixture of fused magnesia, calcined magnesia and a binder suchy as magnesium` sulphate. This materialis rammed in'place around a suitable core which defines thereservoir 24, the- 2 Channel 25 and theducts 27 and28. Preferably a hollow metallic core is used which can subsequently beiilled with molten steel and melted out as described in my raforementioned Patent No. 1,628,375. Surrounding the cru-y cible 23 is a layer of suitable refractory, heat insulating `material29,,such as tire' brick or diatomaceous earth, the whole being enclosed by a metallic Casing 30. A kmetallic shell 31 surrounds the furnace and av member32 of refractory material forms a cover for the reser- Avoir24.1The.coverxnemher 32 may be supported any suitable'` manner and is shown jas resting on angle irons 33' attached to the 34 serve to A'metallic, tubular member 35 surrounds the 'primar winding 26 and between this tubular mem er 35 and that part of the Crucible 23 containing the Vchannel 25V is a la er of compactedV granularl material 36 similar to the material forming layers 20'and v2v2 shown in Fig.` 11 A- la er of granular material 36a also is provide Y Crucible 23 and the refractory material 29 and falso surrounds the outer portion of that part of the crucible'containingthe channel' 25.y Non-magnetic Cooling tubes y37 are provided, as in Fig. 1,*and these tubes serve the dual purpose of aiding in. packing the granular material and in cooling lthis material when the furnace is in operation in a manner similar tofthat used inthe Vfurnace shown in .Figli Y y The furnaceiis -flrferably mounted on 'suitable rockers 39" w ich rest on vtracks 40, and

itmay be tilted by-,mean's ofa suitable hy- `dlaulicmotor 41 inorder to pour metal from the furnace. This is described and explained more clearly in my Patentlllo 1,628,375 hereinbefore referred to;

the Crucible 23 orin'that part o f the vCrucible will be stop Yed when yit reaches the junction of the cruci le23l and the packed, granular between the' bottom of the shouidpmetal leaks sur. in the beam ofV 1 containing thechannel 25,l the flowing' metal material 35, 36a. It will be observed that the granular material 2O and 22 of the furnace shown in Fig. 1 and the granular material 36, 36a of the furnace shown in Fig. 2 perform two functions, that is, the granular material assists in absorbing expansion between the crucibfles and the cuter refractory layer and, secondly, the granular material serves to stop metal leaks occurring in the crucibles.

While I have described my invention as einbodied in concrete form and operating in a specific manner in accordance with the rovisions ofy the patent statutes, it should understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, 'the scope of which is set forth in the annexed claims. l

4What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of packing a furnace Crucible so as to prevent metal leakage therefrom 'which consists in surrounding said crucible with a layer of anulated, refracto heat insulating material and agitating sai material while applying it to said Crucible so as to compact the material tightly against the crucible.

2. The method of packing a furnace crucible so as to prevent metal leakage therefrom which consists in surrounding said crucible with a layer of granulated, refractory, heat insulating material and heating said crucible while applying said materia 3. The method of packing a furnace cruclble so as to prevent metal leakage therefrom which consists in surrounding said crucible while heated with a layer of granular heat refractory material. 4. The method of packing a furnace crucible so as to prevent metal leakage therefrom which consists in surrounding said Crucible with a layer of granular heat refractory material, the material being agitated as it is applied to the Crucible.,

" 5. The method of packing a'furnace crucible so as to prevent metal leakage therefrom which consists in surrounding said Crucible with a layer of fused magnesia grains, heating said Crucible while applying said magnesia, and agitating saidmagnesia while applying it to said crucible so as to compact the grains into a dense mass against the crucible.

6. The method of packing a furnace crucible so as to prevent metal leakage therefrom whichconsists in spacin a plurality of rodlike members at interva s around said crucible, and then surrounding said crucible while heated with a laKer of heat refractorymaterial, said rod-li e members being vibrated Vas said material is being applied to said crucible whereb said material is packed tightl (against sald crucible.

7. The met of packing a furnace crucible so as to prevent metal leakage therefrom which consists in surrounding said Crucible with a plurality of non-ma etic tubes, heating said Crucible, surroun ing said Crucible while heated with a layer of granulated, refractory, heat insulating material and vibrating said tubes while ap lying said material to said Crucible whereby said material is packed tightl against said Crucible.

8. The met od of packing a furnace Crucible so as to prevent metal leakage therefrom which consists in surrounding said Crucible with a layer of granular heat refractory material, heating said Crucible while applying said material, and intermittently agitating sali3 1i material while applying it to said cru- Ci e.

9. The method of packin a furnace lcrucible so as to prevent meta leakage therefrom which consists in surrounding said cru- Cible with a layer of ranular heat refractory material, heatin said Crucible while applying said materia and intermittently agitating said material While applying it to said Crucible during the interval in which said Crucible is expanding due to rising temperature.

' In Witness whereof, I have hereunto set my hand this 15th day of A ril, 1930.

MA NUS UNGER., 

